For obvious reasons related to safety, comfort and route-planning, operators of mobile vehicles require accurate real-time weather information. Depending upon the type of mobile vehicle, the weather information can be necessary for situational awareness, tactical planning, resource protection and operational safety. For example, aircraft pilots require timely and accurate weather data to make informed decisions during both the pre-flight planning process and while in flight. For flight planning purposes, the pilot needs to know current weather conditions at the departure location, and forecast weather conditions for the intended route of flight and the planned destination. Once en route, the pilot should maintain real-time awareness of actual and forecast weather conditions for the remaining flight route and also the intended destination and alternative destinations.
Several weather information delivery systems are available today, primarily intended for aircraft. Generally these systems do not provide coverage for vehicles operating on the ground or at low altitudes. Such systems require the construction of hundreds of communications ground stations, representing a considerable up-front investment, to provide service to users. Also the range of these systems is limited. Available satellite-based systems offer lower up-front costs, but typically cover only the land mass of the continental United States, and therefore are not available to ocean-going vessels.
Disadvantageously, the known weather information communications systems operate at relatively low data rates (for example, 9600 bps), thus requiring several seconds or even minutes to download image-based weather data. Higher data rate systems (up to about 31,500 bps) are available, but these require the use of expensive receiving equipment. Certain available commercial data communications services charge the receiving user on a per kilobyte or a per image basis. These charging practices, which result in relatively high costs for receiving weather data, disincentivize the non-commercial operator from frequent use for receiving real-time situational weather data.
The weather resources available to an aircraft pilot offer an illustrative example of currently available weather information systems. The present National Airspace System (NAS) weather support system provides extensive weather data for pre-flight planning, and limited weather information during flight. Typically, this weather data is received verbally during the pilot's pre-flight weather briefing. During in-person weather briefings the pilot is provided with weather maps of current and forecast weather conditions. Also, print-outs of weather satellite images and weather radar displays can be provided to the pilot during the briefing. During flight, verbal communications with air traffic controllers offers an opportunity for the pilot to collect up-to-date weather information, although the information is provided verbally and based on the controller's interpretation of available weather information. Also, en route alpha-numeric messages are provided to the cockpit to describe generally the weather en route and at the intended destination, but these messages are available only to airlines and transports equipped with ACARS (Aircraft Communicating Addressing and Reporting System) radio receiving systems.
Commercial aircraft generally also employ an onboard weather radar to determine the weather conditions along the intended en route flight path. Such weather radar systems are expensive, complex and require dedicated structural elements on the aircraft. For instance, a weather radar system requires the installation of a relatively large antenna and consumes a fair amount of aircraft power for the radar transmitter. The weather radar systems provides a view of oncoming weather over a range of approximately 150 miles. The pilot can thus alter his en route path to avoid localized inclement weather when detected by the weather radar and when route deviations are authorized by air traffic controllers.
The availability of en route weather information is also critical to the general aviation pilot, but general aviation aircraft are typically not equipped with a weather radar system. It is known that, for instance, during a four hour general aviation flight over a 500 mile route with thunderstorms forecast at about the halfway point, the National Airspace System weather support system would produce almost 2000 individual weather observations and forecasts that could be used to assimilate a detailed weather information picture during that flight, and thus allow the pilot to avoid the thunderstorms. It is obviously impractical for the pilot to request, receive and assimilate this amount of data directly. Therefore, the conventional practice is for the pilot to concentrate on the weather at the destination (and alternate destinations) during pre-flight planning, while en route weather information is provided ad hoc from on-board observations by the pilot or by way of audio conversations with air traffic controllers during which general comments on the weather conditions are provided.
Thus, general aviation pilots have difficulty obtaining pertinent and timely in-flight weather information to allow them to accurately detect weather trends along the flight route and thereby avoid the inclement weather. As an example, assume the pilot is given weather information and weather maps at the airport prior to departure, for example from Chicago, and also weather information along the route and at the intended destination, for example, Louisville. During the flight of several hours the weather along the flight route and at the intended destination could change drastically. The pilot may learn of these weather changes en route from disjointed information sources, such as air traffic controller conversations, but the information can be incomplete, may lack the desired accuracy and may not be timely.
Weather information can also be periodically collected and provided through a satellite communications system. See for example, U.S. Pat. No. 6,014,606. Weather information is collected from throughout a global region, periodically assimilated and compiled at a central source, sent via a high speed data link to a satellite communications service, up linked to the satellite, and then transmitted to an aircraft in flight. As discussed above, such systems are generally too expensive for general aviation aircraft and further require the installation of specialized satellite receivers and antennas on the aircraft.
Although existing systems provide data and voice communications between the cockpit and ground, none are aptly suited for conveying detailed weather data in the form of weather products. It is desirable to deliver certain of the weather products at a refresh rate of six to ten minutes, especially the weather products that include radar imagery data, since this information is very time-perishable (the typical refresh rate at each radar site is six minutes). Thus a dedicated, readily available and relatively inexpensive weather product communications system would be beneficial.
The use of a television signal vertical blanking interval for transmitting digital audio is well understood by those skilled in the art. See, for example, U.S. Pat. No. 6,330,334, Method and System for Information Dissemination Using Television Signals, and U.S. Pat. No. 5,929,922, Method for Broadcasting Digital Audio Over Television Vertical Blanking Intervals. However, these patents disclose the use of the vertical blanking interval only for the purpose of transmitting audio signals.